Paper eec2013_submission_45 (1) (3)

Month 20xx, Volume x, No. x

International Journal of Chemical and Environmental Engineering

Study of Harvesting Rainwater System for Multimedia University (MMU) S. A. Alkaff*; M. I. Fadhel; Abdulaziz Mohamed Abdi

Faculty of Engineering and Technology, Multimedia University,

Jalan Ayer Keroh Lama, 75450, Melaka, Malaysia

Corresponding Author

E-mail: [email protected]

Tel: +6062523240

Fax: +6062316552

Abstract

Malaysia receives rainfall throughout the year with no definite significant dry period. The average rainfall of Malaysia is

greater than 2000 mm, which is more than enough for developing a feasible system. The country is therefore rich in

water resources when compared to the other regions of the world. In this paper the assessment of the rainwater

harvesting within the Multimedia University Campus, Malacca has been studied. A thorough effort was devoted to

estimate the potential of rooftop rainwater harvesting, from the different buildings within the campus. Assessment of the

rainfall profile in Malacca indicates that, the likely dry days may found through the different months in the years.

Moreover, the increase in temperature within those particular days was found noticeable, which in turn affect the

evaporation rate from the ground. Thus, more necessity for irrigating the plantation is required. The football field within

the campus was selected as a case study. A harvesting model was established to simulate the viability of the system.

Results indicate that a 5 m3 tank size achieve an average of 80% reliability to best serve the purpose of irrigation of the

football field.

Keywords: Rainwater; Harvesting; Irrigation; Dry days.

1. Introduction Rainwater harvesting is the collection of rainwater by the

use of a catchment (e.g. roof) which in turn is directed by

a system, comprising of gutters, pipes and filtration,

which eventually lead to a storage container for

consumption. The rainwater that is collected can be used

for a variety of applications which could include toilet

flushing, washing clothes and gardening. When treated

properly, it can be used for drinking as well. The concept

of harvesting rainwater in the event of scarcity is not

entirely a new idea. Ancient civilizations of ancient Egypt

and Jordan have used rainwater harvesting for crop

cultivation among other uses [1-2]. In Japan, the

government decided to subsidize its citizens to help and

encourage the transition to a greener alternative [3],

whereas Singapore are already self sufficient with 60% of

their total water consumption coming from rainfall and

treatment facilities alone. By 2061, Singapore will reach

the deadline of their water agreement with Malaysia and

are well on course in being self-reliant until then in terms

of water supply [4]. In New South Wales – Australia, the

government subsidizes the ownership of all rainwater

tanks purchased after the year 2007. The subsidization is

based on the sizes of the tanks that are purchased and any

household owner is able to apply for them [5]. With

precipitations of 330 mm annually within the Gansu

province - China, old harvesting systems became obsolete

with the rise in population and new research began in the

1980s due to water scarcity. This resulted in improved

farming practices that were immensely benefited by the

locals. The research was initiated by an experiment

conducted with only 16 green houses which later, due to

its enormous success, progressed to 200,000 farmers by

1994. With the increase in participation from the locals

within the province the rainwater harvesting projects

proved to be sustainable with 70% of the investments

coming from the locals themselves [6]. Since Malaysia is

a tropical country which is situated in a strategic location,

it receives rainfall throughout the year with no definite

significant dry period. The average rainfall of Malaysia is

greater than 2000mm which is more than enough for

developing a feasible system [7]. These facts would bring

one to the realization that rainwater harvesting should be

considered as a viable option for the consumption of

water within Malaysia but unfortunately that is not the

case. Rainwater harvesting awareness campaigns have

only begun after the shortage of water that the country has

faced owing to the water crisis in 1998. Due to the “El

Nino” phenomenon which has affected the region, the

level of water in three reservoir dams within Klang Valley

mailto:[email protected]

Preparation of Papers in Two-Column Format for International Journal of Chemical & Environmental Engineering

2

have dropped resulting in a large conservation and

rationing of water by the locals [8]. In this paper the

assessment of the rainwater harvesting within the

Multimedia University Campus, Malacca has been

studied. The objectives of this study are: to estimate the

potential of rooftop rainwater harvesting within the MMU

Melaka campus; to conduct a case study for irrigation of

football field in campus; and to determine the sizing of

the rainwater tank and its placement.

2. Methodology

2.1 Rainfall data

The rainfall data was acquired from a nearby

meteorological station which was in close vicinity to the

campus. Within the station there were two methods of

detecting rainfall, the traditional method by using a bottle

as a rain gauge and the more advanced AWS automatic

weather station’ method. The station only had available

data for four years’ worth of data (Jan 2008 – Dec 2011)

but which contained day to day precipitations along with

evaporation and humidity levels. Other rainfall data was

collected from the Tangki Nahrim program which was

developed by the National Hydraulic Research Institute of

Malaysia. Present within the program, are the average

monthly and annual precipitations starting from 1986 up

to 2006. Statistical formulas were also used in order to

obtain results regarding the daily capacity that could be

gathered. Table 1 shows average monthly rainfall from

1986 – 2006, Malacca Malaysia. While, Table 2 shows

the number of dry days (2008–2011) in Malacca,

Malaysia.

Table1: Average Monthly Rainfall from 1986 – 2006,

Malacca, Malaysia

Month Average Rainfall (mm)

Jan 34.3

Feb 70.3

Mar 142.4

Apr 179.2

May 180.4

Jun 177.1

Jul 217.4

Aug 202.9

Sep 189.6

Oct 196.1

Nov 225.3

Dec 150.3

Table 2: Number of Dry Days 2008 – 2011, Malacca,

Malaysia

Days Without Rainfall

2008 2009 2010 2011 Average Total

Jan 16 24 19 13 18 72

Feb 20 16 17 23 19 76

Mar 9 8 17 16 12.5 50

Apr 12 15 14 11 13 52

May 14 18 19 17 17 68

Jun 11 19 13 13 14 56

Jul 16 16 12 18 15.5 62

Aug 15 12 10 15 13 52

Sep 11 13 11 14 12.25 49

Oct 13 16 14 10 13.25 53

Nov 10 7 7 5 7.25 29

Dec 12 15 16 12 13.75 55

Total 159 179 169 167 168.5 674

2.2 Catchment area

As regards to the area of the rooftops, Google Earth was

utilized at first in order to calculate the rooftop area. The

image was subsequently compared with a template

obtained from Faculty and Management Division (FMD),

Multimedia University in order to identify the measure of

accuracy of the program. The result came to contain a

minor error with the original rooftop length being 68000

mm and the Google Earth result coming to a close 67.4 m

or 67400 mm. This resulted in an error of 0.88% which

was very low. Figure 1 shows Faculty of Engineering and

Technology (FET) rooftop area measurement, using

AutoCAD.

Figure 1: FET Rooftop Area Measurement, using

AutoCAD.

The amount of rainwater that is to be collected “V” can be

calculated by the catchment surface which used as given

in equation 1 [9],


3

(1)

Where V is total rainwater collection (m

3), A is surface

area (m2), Y is precipitation (mm), and RC is runoff

coefficient. RC depends on the catchment surface. A is

the total area of the catchment surface and Y is the daily

rainfall. The three most common catchment surfaces are

tiles, corrugated metal sheets and concrete. Table 3 shows

type of roof surface along with run-off coefficient [10].

There were two types of rooftops within the MMU

Malacca Campus; the first was metal corrugated rooftops

while the other was concrete. The following table

describes the buildings with their corresponding rooftops.

Table 4 shows the buildings with rooftop material and

steepness.

Table 3: Type of Roof Surface along with Run-off

Coefficient [10]

No. Type of Roof Surface Run-off Coefficient

1 Tiles 0.8-0.9

2 Corrugated Metal Sheets 0.7-0.9

3 Concrete 0.6-0.8

2.3 Storage tank sizing

The sizing of the tank was selected based on the

necessities of water required by the football field within

the MMU Malacca campus. According to FMD, the

present field requires an irrigation amount of 1000 liters

per day, not including the natural replenishment received

from rainfall. This sizing is carried out by running a

simulation using MS Excel where economical and

meteorological factors are considered in the final

selection of the tank size. Also an important relation used

was the reliability factor which signifies the efficiency of

the rainwater harvesting system as a whole. It can be

defined as,

(2)

To calculate the tank capacity, an equation was

subsequently formulated based on the pattern of rainfall

and consumption of water by the football field.

Accordingly, constants were also placed within the

equation to keep the utilization of the tank as realistic as

possible. The equation is as follows,

(3)

Table 4: Buildings with Rooftop Material and Steepness

No. Buildings Rooftop Steepness

1 Block A (FBL) Concrete Flat

2 Block B Concrete Flat

3

Administration

Building

Metal

Sheets

Slight

Angle

4 FOSEE

Metal

Sheets

Slight

Angle

5 CITS 1 Concrete Flat

6 CITS 2 Concrete Flat

7 FET

Metal

Sheets

Slight

Angle

8 Main Hall & LP Concrete Flat

9 Plaza Siswa

Metal

Sheets

Slight

Angle

10 Law School

Metal

Sheets

Slight

Angle

11

Block T (Security

Office)

Metal

Sheets

Slight

Angle

12 FIST 1 Concrete Flat

13 FIST 2 Concrete Flat

14 Mosque Concrete Flat

15 CLC Lecture Complex

Metal

Sheets

Slight

Angle

16 CLC Auditorium 1 & 2

Metal

Sheets

Slight

Angle

17 CLC Auditorium 3 & 4

Metal

Sheets

Slight

Angle

18 Library

Metal

Sheets

Slight

Angle

Where x is previous day's capacity, A = 0 if tank's full,

B = 0 if tank <1, y is total rainfall received, z is daily

consumption and equal to 1m3, α is volume needed for

full capacity = tank size – x, θ = 90o when there is RF and

θ = 0o when there is no RF, and φ = 90

o when y<α and φ

= 0o if y>α.

2.4 Payback period

Payback period for harvesting rainwater system can be

calculated as:

(4)

The value of water saved can be defined as:

(5)

The total water saved can be express as:


4

3. Results and Discussions

3.1 Rooftop area

The areas of the rooftops around campus were calculated

using AutoCAD program (Figure 1). The area was

calculated with relative ease by using the area function

present within the program. All the rooftops within the

campus are displayed along with its respective area

(Table 4). There are two types of buildings present within

the list, either concrete or metal. For future concerns, the

metal based rooftop could produce water that can be

suitable for drinking (after appropriate treatment) as well

as other domestic applications, whereas the concrete

based rooftops are only suitable for irrigation purposes.

With the help of these roof catchment areas, an overall

potential of rainwater collection volume can be calculated

with the help of the average monthly rainfall (Table 1)

multiplying with a runoff coefficient of 0.8 due to

concrete and metal rooftops, we get a potential of 2720.7

m3.

3.2 Humidity and evaporation

From the daily meteorological data (Table 5), it is

apparent that the evaporation rate is highly affected by the

temperature, humidity and daily total solar radiation. The

lower the humidity level, the higher the evaporation rate

because of the tiny amount of water present within the air.

This fact shows that more irrigation is required with days

with less humidity levels due to the increase in

evaporation.

3.3 Elevation and tank placement

By reviewing the campus in a more geographical

perspective, it is quite clear that there is considerable

variation between the elevations of the buildings with

respect to the football field. The MMU Malacca campus

is constructed along Bukit Beruang which is a hill situated

adjacent to the campus. In the Figure 2, the difference in

elevation is calculated by the use of Google Earth for the

FOSEE building and the football field within campus.

The highest and lowest points come at the ends of the

white line that can be seen within the Figure 2. The first

end coming out at 22m was located at the football field

while the other end was at 36m. The latter point wasn’t

placed at the roof of the FOSEE building but to the

adjacent parking lot at ground level. The difference

between the elevations came out to be 14m. FOSEE was

chosen as a subject of study because of its considerable

roof capacity and its favorable location, which was the

highest when compared to other buildings within campus.

Due to these factors, suitable and ease of delivering the

water to the field by gravity, eliminating the use of pump.

The placement of the tank was chosen at the parking lot

next to the building serving adequate space and height for

water delivery to the field as can be seen in Figure 2.

Table 5: Humidity and Evaporation Rate, Jan 2009,

Malacca

Day Humidity % Evaporation [mg/(m2.s)]

1 87 2

2 66 5

3 89 1.1

4 59 3.5

5 49 4.6

6 49 6

7 55 5.8

8 52 5.4

9 56 7

10 60 3

11 59 5.2

12 53 5.8

13 60 7.4

14 54 7.1

15 53 7.3

16 49 7.9

Figure 2: Elevation between FOSEE and Football Field

and Tank Placement, Google Earth


5

3.4 Pipeline

Figure 3 shows the route from the tank to the football

field. The route utilizes the rain water drain system within

campus therefore no excavation of any kind is required.

With an elevation of 14 m enough water flow can be

achieved in order to irrigate the field. This could

minimize the expenditure on pumps and the eventual

consumption of electricity for the system. With the help

of the elevated terrain the field could be irrigated with the

help of gravity alone.

Table 6 shows the piping details for the route from

the tank to the football field. The dimensions were

calculated using a pipe flow calculator known as the Pipe

Flow Wizard. This program helps in calculating desired

flow, pressure, diameter and length of a piping system. It

was user friendly where certain values of the system had

to be entered initially to obtain the desired parameter. A

standard inner diameter of 52 mm ‘Rigid PVC Pipe’ was

selected in order to obtain a flow of at least 11 m3/hr

(standard domestic flow rate). Also the length of the route

was entered as 284 m. The elevation from the inlet to the

exit was 14 m as mentioned earlier (elevation between

FOSEE and the football field). The eventual flow rate that

was calculated came out to be 16.488 m3/hr with a fluid

velocity of 2.157 m/s. This was found satisfactory in

terms of irrigation therefore eliminating the use of a

pump.

Figure 3: Pipe Route from Tank to Football Field

3.5 Rainwater tank sizing With the help of Excel a realistic approach was taken in

regards to the effectiveness of the rainwater harvesting

system and the amount of days the tank would in fact

irrigate the football field. Also, a much more detailed

analysis was conducted as to how much water would

actually be saved. The year 2009 (Table 2) was taken as a

sample to conduct the analysis out of the other three years

due to its elongated dry days which can be seen from

Table 2 as 179 days, which is 49% of the entire year. The

flow chart for the simulation of the tank is shown in

Figure 4.

Table 6: Piping Details, Tank to Football Field

Pipe material Rigid PVC

Internal diameter 52 mm

Internal roughness 0.005 mm

Length 283 m

Pipe fittings 12

Standard 90o bend 8

Elbow 45° 3

Gate valve (100%) 1

Total 'K' value of

fittings 5.33

Elevation change 14 m Fall

Flow 16.488 m³/hr

Fluid Water @ 20°C (68°F)

Flow type Turbulent

Reynold's number 111699

Friction factor 0.018

Fluid velocity 2.157 m/s

Figure 4: Flow Chart for Simulation of Tank

With the help of the equation 3, the tank’s behavior was

computer-generated using MS Excel. The most obvious

solution was to choose a tank with the highest reliability

rate. But that may deem financially unsuitable. Therefore,

lists of tanks sizes along with their prices were compared


6

to the amount of water that was being saved. This helped

calculating the payback period of the tank. Table 7 shows

the tank sizes with reliability and payback period.

From Table 7 it can be observed that the cost of the tanks

increases with size. This however was not the same when

the payback period was concerned. It could be seen that

the fastest return was delivered by the 5 m3 tank. This was

due to high reliability rate and increased water savings but

lower costs. The maximum reliability is held by the 10 m3

tank however it gives the second worst payback period. It

should be noted that although the 10 m3 tank is quite

capable, the savings that were produced were only RM

36.4 more annually than the 5 m3 tank. By looking at the

high number of dry days within the year which is the most

out of the other three, it would be easy to assume that the

10 m3 tank would irrigate much more days due to its

much larger volume. But on the contrary, it only exceeded

in irrigating by a mere 28 days than its counterpart which

is twice its size. This proves that lower sized tanks,

although cheaper cannot pay back their investment quick

enough and higher sized tanks, although larger in capacity

do not irrigate at a much higher rate. Therefore the right

size of the tank should serve the purpose of irrigation well

enough and also payback its investment at the quickest

time.

Table 7: Tank Sizes with Reliability and Payback Period

Tank

Size

(m3) Reliability Savings

Tank

Cost

P.B

Period

(years)

1.5 32%

RM

83.20

RM

2,035.20 24.46

2.55 52%

RM

137.80

RM

2,210.10 16.04

3.275 65%

RM

170.30

RM

2,639.40 15.50

4.2 71%

RM

185.90

RM

2,957.40 15.91

5 78%

RM

205.40

RM

2,893.80 14.09

10 92%

RM

241.80

RM

4,801.80 19.86

4. Conclusions

The assessment of the rainwater harvesting within the

Multimedia University Campus, Malacca has been

studied. The case study is carried out based on the

football field within campus. The field consumes 1 m3 of

water every non-rainy day. According to the results, the

catchment size for the FOSEE building which comes to

about 1214 m2 was adequate for collection of rainwater.

The sizing of the tank at 5 m3 is most beneficial in terms

of pay-back and reliability.

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ancient civilizations in Jordan,” Water Science &

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[3] A. Chen-Ani, "Rainwater Harvesting as an Alternative

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[4] UNEP, "Rainwater Harvesting And Utilisation: An

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Urban Water Management: An Introductory Guide

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http://www.unep.or.jp/ietc/publications/urban/urbane

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[6] L. P. Onn, "Water Management Issues in Singapore,"

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[7] Joneikifi, "Flickr," 27 09 2008. [Online]. Available:

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[8] J. D. Sehgal, "A Guide to Rainwater Harvesting in

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